Refactor qmk_install.sh (#10681)

util/install/macos.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+_qmk_install_prepare() {
+    echo "Checking Homebrew installation"
+
+    if ! brew --version >/dev/null 2>&1; then
+        echo "Error! Homebrew is broken or not installed."
+        echo "Please run \`brew doctor\` or follow the installation instructions at https://brew.sh/, then re-run this script."
+        return 1
+    fi
+
+    brew update && brew upgrade
+}
+
+_qmk_install() {
+    echo "Installing dependencies"
+
+    # All macOS dependencies are managed in the Homebrew package:
+    # https://github.com/qmk/homebrew-qmk
+    brew install qmk/qmk/qmk
+
+    brew link --force avr-gcc@8
+    brew link --force arm-gcc-bin@8
+
+    python3 -m pip install -r $QMK_FIRMWARE_DIR/requirements.txt
+}